I'm guessing your PDF is using a spot color blue and your printer is not able to properly render it. Go to Tools> Print Production> output preview (Acrobat 10), Do you see a spot color separation? If yes, go to Tools> Preflight> PDF fixups> Convert to CMYK, Save. If you have the option, convert the spot color to CMYK before saving (or exporting) to PDF. It's also possible you have a mix of RGB and CMYK in your PDF, if so, one of the PDF fixups might help.